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The interaction of vanadium and nickel in USY zeolite has been investigated by X-ray diffraction, nitrogen sorption, Fourier-transform infrared spectroscopy, temperature-programmed reduction, and n-hexane cracking reaction. There is an interaction existing, either direct or indirect through nonframework aluminum, between vanadium and nickel. This leads to the inhibition effect for vanadium and nickel...
A flow cell was used for the monitoring of the state of copper ions in Cu-ZSM-5 in situ at high temperatures by e.s.r. Reduction of the most reactive square-planar coordinated Cu 2+ ions to Cu + occurs at 500°C in methane flow. The reoxidation of cuprous to cupric ions at 500°C by NO or O 2 is very fast; and, at 500°C, in mixtures of CH 4 with excess oxygen,...
A flow cell was designed for the monitoring of the state of copper ions in Cu-ZSM-5 in situ at high temperatures by e.s.r. In thoroughly purified He or in vacuum there is no spontaneous reduction of the cupric ions up to 500°C. The formation of adsorption complexes between isolated Cu 2+ cations and NO molecules at 20°C leads to a measurable change in coordination. Strong adsorption...
The samples obtained during ball milling of zeolite ZSM-5 were characterized by different methods such as X-ray diffractometry, scanning-electron microscopy, FTi.r. spectrometry, and simultaneous thermal analysis. The milling caused considerable change of morphological and particulate properties followed by loss of crystallinity of the treated zeolite. The loss of crystallinity is caused by breaking...
MCM-22 has been synthesized as a unique phase and with good crystallinities in a range of different SiO 2 Al 2 O 3 ratios using hexamethylenimine as a template. ForSiO 2 Al 2 O 3 ratios around 30, MCM-22 can be obtained as a pure phase and with good yields in a relatively broad range ofOHSiO 2 ratios, although the efficiency in Si incorporation...
Microwave heating is applied to the synthesis of AIPO 4 -5. After 60 s of heating, large AlPO 4 -5 crystals are obtained. XRD, polarization microscopy, and adsorption measurements prove the regularity of the AFI framework. In an optimized microwave synthesis prismatic AlPO 4 -5 crystals up to 130 μm long and 40 μm thick could by synthesized. In a two-step synthesis, however,...
A novel method of measuring diffusion in small (micron-sized) zeolite crystals has been developed based on measurement of the chromatographic response for a capillary column, the internal surface of which is coated with an incomplete monolayer of the zeolite crystals. Special techniques are needed to prepare such a column; in the commercially available wall-coated zeolite columns the surface coverage...
NaZSM-48 has been synthesized successfully in a pure solid system of Na 2 O-SiO 2 -Al 2 O 3 -H 2 N(CH 2 ) 6 NH 2 . This method greatly increased the yield of products and decreased the pollution of waste liquid. XRD patterns and data of the as-synthesized sample closely matched those of ZSM-48 synthesized hydrothermally. The sample...
Isotherms of five n-alkanes: propane, butane, pentane, hexane, and heptane in 13 X zeolite have been measured by microgravimetry. In temperature ranges in which the isotherms are reversible, the sorption is described by the statistical model developed by Dupont-Pavlovsky, showing that the sorbed phase is localized. The heat of sorption and the sorbate-sorbate interaction, obtained from the model,...
This paper describes the preparation and characterization of new PILC materials with mixed pillars of Cr 3+ and Al 3+ intercalated between the layers of montmorillonite. Various CrAl ratios were studied to obtain the most suitable physicochemical products. The resulting materials showed basal spacing between 2.49 nm and 1.90 nm for air-dried samples and surface areas between...
The connectivity-configuration matrices method, developed in Part I, is applied to mordenite (Na 8 Al 8 Si 40 O 96 ) to determine the ordered distribution of Al atoms in its framework. There are, in such a high-siliceous zeolite, hundreds of candidates which well describe an observed 29 Si MAS n.m.r. spectrum. By utilizing dependencies of various...
Grand canonical Monte Carlo simulations were used to study the effect of dealumination on adsorption of xenon in an idealized structural model of Na-mordenite. Simulations were carried out at SiAl ratios of 5, 11, and ∞, chosen to represent prototype cation occupancies. A recent experimental study of xenon adsorption in mordenites with different SiAl ratios found unexpected nonmonotonic trends....
Isothermal and isobaric adsorptions of p-xylene and m-xylene on NaY, KY, and BaY are studied by thermogravimetry between 25°C and 400°C, and 10 Pa and 1014 Pa. At low filling BaY shows a stronger affinity for xylenes than the other zeolites. At high temperature and low pressure its adsorption capacity is greater than those of NaY and KY. These two zeolites have a similar behavior and adsorb more...
We report on the synthesis and single-crystal structure of a novel cobalt-substituted aluminophosphate. Crystal data: monoclinic, space group P2 1 c (no. 14), a = 8.593(1), b = 15.540(1),c = 7.736(1) , β = 110.65(1)°, V = 966.7(4) 3 , Z = 4, R = 0.037, and R w = 0.029 for 2280 contributing reflections and 182 variables. Refined framework-atom bond distances and angles exhibited...
Long-term adsorption measurements in the system p-ethyltoluene/H-ZSM-5 zeolite have been performed in the temperature range 303-393 K under constant pressure conditions. The corresponding adsorption isotherms and kinetic data are presented. For temperatures higher than 333 K adsorption isotherms exhibit irreversible features. Kinetic curves show strong deviations from the behavior described by...
Zeolite Y and ZSM-5 were grown on different type of metals and alloys. The influence of chemical composition and surface imperfections of substrates on zeolite film formation was investigated. The results show that the characteristics of metal support determine the zeolite film properties, the size of the zeolite crystals, and the thickness of the coating. The chemical and plastic pretreatment...
EMT- and FAU-type zeolites were prepared by using a mixture of organic molecules, i.e., crown-ether + ethylene glycol or crown-ether + 1,3,5-trioxane. The products were characterized by elemental analysis, XRD, SEM, thermal analysis, n-hexane adsorption, and n.m.r. spectroscopy. Depending on the method used to prepare the starting gel, the solids obtained showed different characteristics. D.t.a...
Titanium silicates with the ZSM-48 structure have been synthesized using a new templating molecule, the trimethylpropylammonium cation. The crystallization period was relatively short compared with that observed with hexamethonium cations. This synthesis route allowed the preparation of zeolites with 1.5 Ti/unit cell, which is the highest value ever reported for this structure in the literature.
Several CoAPO-type materials were obtained by hydrothermal crystallization of gels containing triethylamine as template and variable amounts of cobalt. The nature and crystal morphology of the several crystalline phases were found to depend on the cobalt content of the gel and the crystallization time. AFI and CHA topologies and unidentified phases were obtained. Microprobe analysis coupled with...
Silica gels containing tetraalkylammonium bromide (TAA), hexamethonium (HM) bromide, and 1,2-diaminododecane (DADD) have been prepared in fluoride medium: 10 NaF - (x TAABr -y HMBr 2 - z DADD) - 10 SiO 2 - 330 H 2 O with x + y + z = 1.25. TAA = tetramethyl-, tetraethyl-t tetrapropyl-, and tetrabutylammonium. Silicalite-1 (with TPA), silicalite-2 (with TBA), and ZSM-48 (with...
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